4 Tabular Data

Previously, we learned how to work with bivariate data, working with each individual data point. Here, we view two-dimensional data where each dimension has been summarized into several discrete categories. We refer to this summary as a table and the data as tabular data.

Learning Objectives

• Learn how to represent and analyze tabular data.
• Learn about Simpson’s Paradox, one of the dangers of not controlling for confounding variables.
• Learn about sensitivity and specificity in tests, particularly medical diagnoses.

Useful Functions

• Use matrix() to create a matrix or two-way table.

• Use barplot() to make a bar plot.

• Use mosaicplot() to make a mosaic plot.

• Use margin.table() to calculate the marginal distributions of a table.
• Use prop.table() to calculate the joint and conditional probabilities of a table.

• Use chisq.test() to perform a chi-squared test.